-charles percy shrewsbury



T STATES ATEN'I CHARLES PERCY SHREWSBURY, OF LONDON, AND JOHN LASKEY DOBELL,

' OF MODBURY, ENGLAND.

MANUFACTURE OF CARBON FOR ELECTRICAL PURPOSES.

SPECIFICATION forming part of Letters Patent No. 538,289, dated April 30, 1895.

' Application fil d September 10, 1894. Serial No. 622,645. (No specimens.)

T0 ztZZ whom it may concern.-

Be it known that vwe, CHARLES PERCY SHREWSBURY, engineer, residing at No. 8 Furnivals Inn, in the city of London, and

JOHN LAsKEYDoBnLL, electrician, residing at Traine, Modbury, in the county of Devon, England, subjects of the Queen of Great Britain, have invented certain new and useful Improvements in the Manufacture of Carbon for Electrical and other Purposes, of which the following is a specification.-

This invention relates to improvements in the manufacture from carbonaceous matter of plates, slabs, pencils and other articles for electrical, and other purposes.

In manufacturing some of the articles of the kind above referred to graphiteis usually taken as the best material for the purpose on account of its even and fine texture, but it is very costly and can therefore generally only be employed in cases where the expense is not a serious matter.

Now, the object of the present invention is to produce carbon articles, from a novel compound which, when treated in a particular way, produces a material which is an electrical insulator while when manufactured under other conditions it is equal or superior to graphite as an electrical conductor, and, at at the same time, the cost thereof is considerably less. For this purpose, the compound employed in the above manufacture consists of anthracite coal, bituminous coal and tar or pitch or a mixture of tar and pitch, and the articles which are formed from such mixtureare submitted to pressure and to a gradual baking and cooling process as hereinafter more fully described.

During the baking process above referred to, certain ingredients, for instance, hydrocarbons, of the coal are driven off, and in the absence of tar or pitch or a mixture thereof the density of the finished material which is of paramount importance'would be too small, but the addition of the tar or pitch to the coal binds or assists in binding the same into a cohesive mass, if added in proper proportions, and compensates for the'hydro-carbons driven off.

The bituminous coal best suited for the purposes of this. invention is that kind which will readily cake, that is to say, such as will in the presence of heat swell, andtheu become as it were fused into a mass. The less freely the coal becomes caked when submitted to heat the less suitable is it for the purposes of this invention.

The anthracite coal and bituminous coal are first reduced to a fine state of division and then placed in a suitable mixing ma chine in or in about the following proportions: anthracite coal, ten parts by weight; bituminous coal, four parts by weight; and after having been thoroughlymixed, a suitable quantity of tar or pitch or tar and pitch is added thereto but such quantity may be varied according to the caking quality of the bituminous coal and the degree of pressure to be employed in forming the material into the required shape, as hereinafter described.

It the bituminous coal be of good quality, that is to say, good caking quality, about seven parts by weight of tar or pitch or tar and pitch may be added to the mixture of coal above given and a light pressure may be employed, that is to say, a pressure not exceeding twenty pounds to the square inch.

The poorer the caking property of the coal, the greater must be the proportion of tar or pitch or tar and pitch employed in combination therewith, as will be readily understood.

The amount of tar or pitch or tar and pitch employed is reduced if the pressure used in forming the articles is increased say to one hundred pounds'or upward to the square inch.

The material consisting of the coal and tar or pitch or tar and pitch having been thoroughly mixed is submitted to a suitable degree of pressure which may be exercised upon the material when placed in suitable molds or by expressing the material through a die, the degree of pressure being varied according to the nature of the materials and the form of the articles required.

When the material is molded under a light pressure, for instance, a pressure not exceeding twenty pounds per square inch it is not sufficiently condensed to retain itsform during the baking process if removed from the molds previous to being placed in the oven;

but in order to avoid this difficulty the articles are baked in the molds and for this purpose the molds with. their contents are placed in an oven and submitted to the baking operation in a covering of ashes, as hereinafter described, after which the articles may be removed from the molds, and, if they are required to have a high electrical resistance, they are ready for use, but, if on the contrary they are required to be of low electrical resistance, they are submitted to another baking at a high temperature, as hereinafter described.

W'hen the material is lightly pressed within the molds as lastly described, the molds containing the material are placed in an oven and covered or embedded in ashes. The oven is then closed and the temperature thereof is raised, the maximum temperature varying with the purposes for which the manufactured articles are required. For instance, if it be desired to produce a plate or other article to be employed as an electrical insulator, the.

maxi mum temperature must not exceed about 1,450 Fahrenheit. duced is required to possess a high electrical resistance the temperature must be above 1,450 Fahrenheit, but must not exceed about 1,600 Fahrenheit. If the material is required for Leclanch or Bunsen batteries and similar purposes the temperature must be above 1,600 Fahrenheit. In all cases the oven is allowed to remain at the maximum temperature for a period of about four hours. If the articles produced are required to be of a low electrical resistance such as the carbon plates required for electrolysis or are to be subjected to a high temperature, the temperature should be raised to from about 1,600 to 1,800 Fahrenheit, and having been allowed to remain at this temperature for a period of about four hours the oven is allowed to cool gradually and when cold the molds are taken therefrom, and the contained articles are removed from the molds or receivers and placed in tiers in an oven with ashes between and surrounding them. The oven is then closed and the temperature thereof is gradually raised to 2,500 Fahrenheit or upward, the maximum temperature being maintained for a period of about four hours. The oven is then allowed gradually to cooldown and the baked articles are removed in a finished state. If, however, the material in the molds be submitted to a pressure of say three hundred pounds or upward per square inch the molded articles may before being placed in the oven be removed from the molds and placed in a drying chamber where the moisture is gradually driven off therefrom by the application of heat, or they might be dried by exposure to a dry atmosphere, or they mightbe sun-dried, after which, even if the article is to be of a low electrical resistance, the baking may be effected at one operation.

If the article to be pro- In lieu of using molds as lastly referred to, when making articles of suitable sections, the materials maybe placed in an expressing machine and expressed through dies, by a suitable pressure, cut into required lengths and dried and baked, as lastly described.

The important feature ot'the material hereinbefore described is that, when exposed to heat, it shrinks or contracts very considerably and equally all over thereby gradually increasing the density thereof. This contraction of the material is very important, and, in order that it. may take. place evenly without causing cracks, breakage or loss of shape, care should be taken not to apply the heat to the middle of the article, when baking, but so to apply the heat that it operates especially on the ends. For the same reason, it is of paramount importance that the temperature of the ovens should be raised and lowered very gradually, as in the operation of baking the contraction of the material is so great that any sudden change of temperature would cause the article to crack or break.

What we claim is 1. In the manufacture of carbon from carbonaceous matter, combining anthracite coal, bituminous coal and tar or pitch or tar and pitch in such proportions as to constitute a material which contracts when exposed to heat, submitting the same to pressure and baking the articles formed therefrom, substantially as herein described.

2. In the manufacture of carbon from carbonaceous matter, combining anthracite coal and bituminous coal in or in about the pro portions given with tar or pitch or tar and pitch, in order to obtain a material which contracts when exposed to heat and submitting the same to pressure and baking the articles formed therefrom, substantially as herein described.

3. In the manufacture of carbon from carbonaceous matter, combining anthracite coal, bituminous coal and tar or pitch or a mixture of tar and pitch all in or in about the proportions given in order to obtain a material which contracts when exposed to heat and submitting the same to pressureand baking the articles formed therefrom, substantially as herein described.

4. In the manufacture of carbon from carbonaceous matter, combining anthracite coal, bituminous coal and tar or pitch or a mixture of tar and pitch all in or in about the proportions given, in order to obtain a material which contracts when exposed to heat, forming the articles therefrom with the aid of pressure and submitting the articles to a preliminary drying or baking operation and finally baking the same at a high temperature, substantially as herein described and for the purposes stated.

5. In the manufacture of carbon from carbonaceous matter, combining anthracite coal,

bituminous coal and tar or pitch or a mixture of tar and pitch all in or in about the proportions stated, in order to obtain a material 'Which contracts when exposed to heat, form- 5 ing the articles therefrom by the aid of pressure and submitting the articles to a preliminary drying or baking operation and finally baking the same, while covered buried in ashes, at or at about the temperatures given to care being exercised to gradually raise and lower the heat, substantially as herein described,

CHARLES PERCY SHREWSBURY,

JOIIN LASKEY DOBELL.

Witnesses:

GEO. S. VAUGHAN, 57 Chancery Lane, London.

ALFRED GERALD TooKs, 5 Emily Street l Vestbourne Square, London. 

